The present invention relates to an apparatus for mounting an electronic component held by a component-holding portion thereof on a circuit substrate at a predetermined position thereof. More specifically, the present invention relates to an apparatus for attaching an electronic component held by a component-holding portion thereof onto a circuit substrate at a predetermined position thereof or an apparatus for inserting the component in a hole of the substrate.
Referring to FIGS. 6-10, an example of a conventional apparatus for mounting an electronic component on a circuit substrate is described below.
Referring to FIG. 6, the apparatus comprises a rotary table 31 which rotates at a predetermined angle intermittently; a plurality of rods 32, vertically movable, disposed around the periphery of the rotary table 31 at regular intervals each corresponding to the predetermined rotational angle of the rotary table 31; and a plurality of nozzles 33, for sucking the electronic component thereto, installed on the lower end of each rod 32. The apparatus further comprises a plurality of mechanical valves 34, provided on the rotary table 31, which turn a vacuum circuit on and off for operating each nozzle 33; a component supply section 35 for supplying the electronic component to an electronic component-sucking position at which it is sucked by the nozzle 33; and an XY-table 36 which secures a circuit substrate 37 thereto on which the electronic component is mounted. The XY-table 36 is moved so that a predetermined electronic component-mounting position of the substrate 37 coincides with the nozzle 33 holding the electronic component. As shown in FIG. 7, the rod 32 is supported to be rotatable and vertically movable by a nozzle unit 38 installed on the rotary table 31. A lever 43 of a cam/lever mechanism 42 is arranged to pivotally move around a shaft 43a. One end of the lever 43 engages a block 41 disposed at the upper end of the rod 32 and the other end of the lever 43 engages a cam 52. Then, the lever 43 pivots in response to the rotation of the cam 52 to move the rod 32 upward and downward through the block 41.
As shown in FIG. 8, as a result of the rotation of the cam 52 of the cam/lever mechanism 42 for moving the nozzle 33 vertically at an angle of 360.degree., during the first half of a predetermined time period in which one electronic component is mounted on the substrate 37, the rotary table 31 rotates a predetermined angle (index period of time) and the XY-table 36 moves so that the predetermined electronic component-mounting position coincides with the position of the nozzle 33 holding the electronic component. During the second half of the predetermined period of time, the nozzle 33 moves downward to mount the electronic component on the substrate 37 and then moves upward.
The above-described index period of time means the .period of time in which the nozzle 33 is at its uppermost position or the period of time obtained by the sum of an appropriate allowable period of time before and after the period of time in which the nozzle 33 is at the uppermost position and the period of time in which the nozzle 33 is at the uppermost position. The movable period of time of the XY-table 36 is set based on the vertical movement of the nozzle 33. That is, as shown in FIG. 9, the movable period of time of the XY-table 36 terminates when the distance H.sub.3 between the lower end of the nozzle 33 and the upper surface of the substrate 37 becomes equal to the sum of the maximum warpage of the substrate 37 and a height which is twice as large as the height of the electronic component 39 of the maximum height, as a result of the downward movement of the nozzle 33 in the distance of h from its uppermost position. As shown in FIG. 10, the movable period of time of the XY-table 36 starts when the distance H.sub.4 between the lower end of the nozzle 33 and the upper surface of the substrate 37 becomes equal to the sum of the height of the electronic component 39 of the maximum height and the maximum warpage of the substrate 37, as a result of the upward movement of the nozzle 33 in a predetermined distance from its lowermost position.
During the movable period of time of the XY-table 36 set as described above, there is no possibility that the nozzle 33 or the very high electronic component 39 held by the nozzle 33 interferes with a very high electronic component which has been mounted on the substrate 37 even though the electronic component 39 is mounted in the vicinity of the electronic component which has been mounted on the substrate 37. However, the movable period of time of the XY-table 36 is short. As a result, the XY-table 36 is required to move a long distance so that the predetermined electronic component-mounting position of the substrate 37 coincides with the position of the nozzle 33 holding the electronic component 39. Then, if those positions do not coincide with each other within the movable period of time of the table 36, the entire period of time for mounting one electronic component on the substrate 37 must be longer. Thus, the apparatus is not efficient.
On the other hand, referring to FIG. 7, a gear 39 for transmitting a rotary force to the rod 32 is installed on an upper portion of the rod 32. A vacuum tube 40 extending from the mechanical valve 34 is connected to the upper end of the rod 32 to operate the nozzle 33. A cylinder 45 for moving a stopper 44 vertically between an upper position and a lower position is provided below the lever 43. The stopper 44 engages the lever 43 of the cam/lever mechanism 42 at the upper position when the electronic component is held in an inappropriate posture by the nozzle 33. In this manner, the downward movement of the block 41 is prevented, i.e., the operation for mounting the electronic component on the substrate 37 is stopped.
The apparatus further comprises a pusher 46 for performing the change-over of the mechanical valve 34 which turns the vacuum circuit on and off for operating the nozzle 33 and a change-over cam/lever mechanism 47 for driving the pusher 46. A cylinder 50 for moving a stopper 49 vertically between an upper position and a lower position is provided below the change-over cam/lever mechanism 47. At the upper position, the stopper 49 engages the lever 48 of the change-over cam/lever mechanism 47, thereby preventing the vacuum circuit from being turned off by the pusher 46. That is, when the electronic component is held in an inappropriate posture by the nozzle 33, the nozzle 33 keeps holding the electronic component.
The above-described conventional apparatus has a complicated construction and is expensive. As a means for preventing the electronic component from being mounted on the substrate 37 when the electronic component is held in an inappropriate posture by the nozzle 33, the apparatus is provided with the stopper 44 which engages the cam/lever mechanism 42 for vertically moving the nozzle 33, the stopper 49 which engages the change-over cam/lever mechanism 47 for performing the change-over of the mechanical valve 34, and the cylinders 45 and 50 for driving the stoppers 44 and 49, respectively.
In addition, the apparatus has a slow response because of the use of the long vacuum tube 40 connecting the mechanical valve 34 and the nozzle 33 to each other.